Bonded Repair of Primary Composite Structures

Composite repairs are difficult and time-consuming activities. It has not yet been properly mapped out what effect the repairs will have on the quality of the material in the long term. A repair method that can offer a solution is the so-called ‘Bonded Repair’. With this method a composite patch is glued in or over the damaged area. According to tests, Bonded Repair has the potential to restore both the rigidity and the strength of the material for 100%. An additional advantage is that the repair can be designed in such a way that the smooth outer contour is retained, so that the composite remains aerodynamic.

Innovation Track 1: Developing a certified composite repair method

In this innovation track our aim is to develop a certified composite repair method. By conducting research into methods for certification of the adhesive bonded repair including the use of Structural Health Monitoring (SHM) systems, a representative demonstrator will be designed, manufactured and tested.

The project focuses on the bolt free repair of aerospace primary structures using composite patches adhesive bonded to the damaged area. The objective is to investigate and define materials and repair processes capable of restoring the operational capability of the damaged structure in compliance with the airworthiness certification requirements.

Project status

Runtime: March 2017 – 2019

  • Milestone 1: Literature review

    As there are many composite materials and repair methods in use a selection of a representative demonstration platform is needed. The repair of a sandwich structure was selected to demonstrate the repair and airworthiness certification of the repair.

  • Milestone 2: Determining the demonstration structure

    As there are many composite materials and repair methods in use a selection of a representative demonstration platform is needed. The repair of a sandwich structure was selected to demonstrate the repair and airworthiness certification of the repair.

  • Milestone 3: Determining the materials and material properties

    The material properties are needed to analyse and design the repair. The properties were partly obtained by literature review and partly by performing mechanical tests.

  • Milestone 4: Determining the certification approach

    As there are no standard certification methods available for adhesive bonded repairs on aerospace structures alternative certification methods have to be investigated. Finally an approach was found were the initial bond strength was substantiated by testing of traveler patches surrounding the repair patch together with an in-service monitoring of the repair patch behaviour by a dedicated SHM system.

  • Milestone 5: Design and analysis of the repair

    Methods have been developed for a quick assessment of the remaining strength of a damaged structure and the restored strength in case of a bonded patch repair. Within this milestone the demonstrator repair was designed and analyzed.

  • Milestone 6: Manufacturing of the demonstration repair

    The repair was manufactured and the repair demonstrator is ready for testing.

  • Milestone 7: Demonstrator test (in progress)

    Execution of the static and fatigue test program.

Partners involved

More information

For any questions about the project (status) or if interested to collaborate, please contact:
Henk Jan ten Hoeve (NLR) Henk.Jan.ten.Hoeve@nlr.nl or Jan Halm (NLR) Jan.Halm@nlr.nl